What is another word for ullage?
Pronunciation: [ˈʌlɪd͡ʒ] (IPA) 
Ullage is a term commonly used in the wine and spirits industry to describe the amount of empty space in a container after it has been filled with liquid. However, there are a number of synonyms for this word that can be used to describe the same concept. Some possible alternatives include headspace, slack fill, air gap, or void. Each of these terms refers to the space in a container that is not occupied by liquid, and all are commonly used in discussions of packaging, storage, and shipping. While ullage may be the most common term, there are many words that can be used to convey the same idea.
